This invention relates generally to stabilizer systems adapted to level the dump body of rear tipping dumping vehicles during unloading. More particularly, the present invention is concerned with stabilizer apparatus which levels the dumping body during unloading while permitting simultaneous manuevering of the tractor unit.
As will be appreciated by those skilled in the art, dumping vehicles comprise a cargo or load body structurally pivoted to the chassis frame of a trailer about an axis substantially parallel to one of the axles of the rear wheels. The dump body chassis may be resiliently supported on appropriate leaf springs associated with suitable shock absorbers. Usually the terrain upon which such vehicles are employed is uneven and rough. Hence, when the dump body is tilted to an unloading position, the trailer may become unstable. This factor is especially aggravated when very long dump bodies are employed on laterally sloping terrain. Since the center of gravity of the dumping body rises as the body is tilted upwardly, stability may decrease dangerously.
A plurality of prior art concepts have been proposed for stabilizing dump bodies during the unloading operation. One system incorporates the idea of locking the rear suspension of the trailer in a predetermined position during unloading. Examples of the latter concept are shown in U.S. Pat. Nos. 3,778,105; 2,999,721; 2,662,780. Hydraulic piston systems for leveling tilting bodies are shown generally in U.S. Pat. Nos. 3,044,832; 3,083,059; and 2,381,425. U.S. Pat. Nos. 2,829,901 and 3,362,299 disclose multi-piston systems wherein truck beds or the like are leveled by various control valves. U.S. Pat. No. 3,331,616 discloses a system wherein a vehicle (not a tilting unloading dumping vehicle) may be automatically leveled as it is loaded with increased weight.
In my prior U.S. Pat. No. 4,216,996 I have disclosed a system for leveling a trailer during unloading which employs a pair of rear mounted hydraulic rams independently controlled by a level sensing pendulum mechanism. Pressure plates are pivoted at the trailer rear and are forced into contact with the trailer wheels by independent hydraulic rams, the lowermost of which is actuated by the pendulum to compensate for level variances. The dump bed is elevated by a single ram extending from the tractor chassis to the underside of the tilt body. Although rear pressure plates stabilize the tilt body during dumping, forcible contact with the rear trailer wheels prevents movement. Therefore, during unloading the tractor may not be manuevered, since the rear wheels are "locked up". I have found that it is desirable to facilitate tractor manuevering during the unloading operation, while at the same time automatically leveling the trailer by a pendulum system which controls a pair of spacedapart tilt rams associated with the tractor. Moreover, by associating the pressure plates with the driven wheels of the tractor, rather than the wheels of the trailer, a number of benefits are achieved.